Now you can put a dispenser in a minecart and power it with activator rails. To my knowledge, these imitate (to varying degrees of accuracy) everything a dispenser does with items except for bone meal. They'll also shoot tridents and place command blocks. They can face forward, backward, off the rails or upward.

Note that there are rendering problems. Shot fire charges will be invisible and dispensed item entities, snowballs, eggs, and potions will take about a second to appear up in the right place. This doesn't affect functionality, just what you see.